This invention relates to an ultrasonic transducer and, more particularly, to the housing that protects the ultrasonic sensor element.
Ultrasonic techniques are widely used to inspect articles. In this approach, an ultrasonic signal is transmitted toward or into the article. The ultrasonic signal that is passed through or reflected from the article is sensed and compared with the transmitted ultrasonic signal. The results yield information about the internal structure of the article and/or the presence of defects such as cracks in the article.
An ultrasonic transducer used in such inspection procedures includes an ultrasonic sensor element that typically is a transceiver which transmits an ultrasonic signal, receives an ultrasonic signal, or both transmits and receives an ultrasonic signal. The sensor element is enclosed within a housing that mechanically and electrically protects the sensor element. For applications where the ultrasonic transducer is to be immersed in water or other liquid, the housing is usually made of stainless steel. There may be some electronic components located within the housing as well. An electrical cable connects to the housing and thence to the sensor element through a feedthrough, to provide electrical communication between the sensor element and the internal electronics, if any, and external driver and/or analysis electronics.
For some applications, the available ultrasonic transducers are too heavy. They cannot be supported and moved properly by the available support structures. This situation most commonly arises where it is desired to inspect two or more areas on the article at the same time, so that two or more ultrasonic transducers arranged as an ultrasonic transducer system must be supported from the same support structure. In one solution to the problem, the housing has been made of aluminum alloy or titanium alloy to reduce the weight of the housing. It has been found that the aluminum alloys corrode over time, producing a hole in the housing, and that the titanium alloys are too expensive.
There is accordingly a need for an improved ultrasonic transducer that is lighter in weight that those currently available, and is also sufficiently sturdy and corrosion resistant that it does not deteriorate over time. The present invention fulfills this need, and further provides related advantages.
The present approach provides an ultrasonic transducer system with an ultrasonic transducer having a housing that is light in weight and fully protects the ultrasonic sensor element mechanically in water immersion and electrically against external radio frequency electrical noise. The ultrasonic transducer system may include single or multiple ultrasonic transducers.
An ultrasonic transducer system has at least one ultrasonic transducer. Each ultrasonic transducer includes a housing having a wall that is made at least in part of an organic structural material that is substantially impervious to water. Polyvinylchloride plastic is the preferred material of construction of the housing. Many other common plastics absorb water, resulting in a change in shape that distorts the assembly, and are therefore not acceptable materials of construction for the housing. An ultrasonic sensor element is located at least in part within the housing and positioned to transceive ultrasonic signals. The housing preferably has a lateral side which is substantially cylindrical in shape. The ultrasonic sensor element is preferably a piezoelectric copolymer film ultrasonic sensor element.
The ultrasonic transducer system desirably further includes an electrically grounded shield within the housing and adjacent to an interior wall surface. The grounded shield is desirably made of an electrically conductive metal.
The ultrasonic sensor element is preferably a piezoelectric copolymer film ultrasonic sensor element. Such an ultrasonic sensor element comprises a backing structure located at least in part within the hollow interior of the housing and having a backing surface facing out of the housing through the open first end of the housing, a backing electrode lying against the backing surface, and a ground electrode overlying the backing electrode. The backing surface is preferably concavely curved relative to the backing structure.
The ultrasonic transducer system preferably includes at least two ultrasonic transducers, with each ultrasonic transducer comprising the structure set forth above. There is typically a support structure upon which each ultrasonic transducer is supported.
In one embodiment, an ultrasonic transducer system has at least one ultrasonic transducer. Each ultrasonic transducer comprises a housing having a wall that defines a hollow interior of the housing and includes a cylindrical lateral side, an open first end, and a closed second end. The wall is made of polyvinylchloride plastic. An electrically grounded shield is within the housing and adjacent to an interior wall surface of the lateral side of the housing. The grounded shield is made of an electrically conductive metal. An ultrasonic sensor element is located at least in part within the housing and positioned to transceive ultrasonic signals through the open first end of the housing. Features discussed elsewhere herein may be used with this embodiment.
The ultrasonic transducers of the present approach have substantially reduced weight as compared to conventional transducers, due to the use of the water impervious structural-organic housing. The structural-organic housing is not an electrical conductive material that shields the ultrasonic sensor element from external radio frequency signals. The electrically grounded shield provides this protection against external radio frequency signals. The manufacturing cost of the ultrasonic transducer is also reduced due to the use of the structural-organic material.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.